UPDATE FROM MABULA
I have had a very rough 2 months unfortunately health wise. I was struck 3x in a row with bacterial infections. The second infection occurred  after a routine hospital checkup and I became very sick. I had to rest and take a lot of antibiotics. Once I was recovering and restarting work 1 month ago, I again became sick. The infection was not yet gone, so even more antibiotics and rest was needed. Needless to say, it took a lot of my energy and I needed a lot of rest.
Finally, the infection is really gone and my energy is coming back step-by-step now and I have started work again. I am terribly sorry to have kept you waiting for support. I will address all outstanding questions and e-mails step-by step and will be on the forum daily from today.
APP 2.0.0-beta47 will come soon as well, a lot of work was already completed before I became very ill, so the release is also nearly ready for you. Beta47 will be much faster actually. Many workflows will be more than 2x faster, mosaics can even be 10x faster than before because registration really received a major boost... all compared to beta46. Â Before I release it, I will make sure that everything is working properly and then I will release it.
I took 140x120sec subs of IC443. I use a refractor, narrowband filter and OSC camera.
The lights were stacked with darks, flats and darkflats.
In the result I get this strange red halo.
Your help in solving the problem is much appreciated.
Thanks
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Seems like light pollution, is that a possibility in your location? Or, the flats are not correctly applied, can you see (in the list of files below) if MF is added to the filename after calibration?
@vincent-mod
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I'm in a bortle 9 location so light pollution certainly exists.
However, I usually manage to eliminate it.
MF was applied to the subs.
what do you mean by "flats are not correctly applied"?
I was wondering whether a white balanced light source is needed for the flats?
ThanksÂ
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I used a narrowband filter
Flats may not be correctly applied, not saying they are, could just be a cause of what you're seeing. However, when it indeed is light pollution, you can use the light pollution tool that should be able to take care of that nicely. Also, when using a narrowband filter, you need to set APP to extract that data properly, in tab 0 you can select to "extract Ha" for instance. This will produce an Ha, mono image, straight from the OSC data.
When you say halo, are you taking about the ring around the bright star, or are you taking about the redness in the image that seems to appear beyond the nebula, around it? If you are referring to that redness as the halo, I would say you need to do a better job cropping your image first. You can see stacking artifacts around the edges. Crop your image first, then run the LP removal and you will see much better results.
